Improving performance evaluation coefficient and parabolic solar collector efficiency with hybrid nanofluid by innovative slotted turbulators

The goal of the present work was to define a new geometry of the twisted strip that could lead to the improvement of efficiency (η) in the solar collector (SC) by increasing heat transfer rate (HTR) and decreasing pressure drop (ΔP). CuO-SWCNT/water hybrid nanofluid has been used in nanoparticles volume fractions (ϕ) of 1% to 4%. The study was implemented in single phase for the Reynolds number (Re) varying from 4000 to 10,000. The governing equations were solved by the finite volume method (FVM), using the k-ω-SST turbulence model and SIMPLEC algorithm. Two samples of twisted strip with v-shaped cuts in different numbers and placement angles were investigated. The findings revealed that the highest efficiency in the pipe was related to the twisted strip with three v-shaped cuts equal to 2.46; meanwhile, for the pipe with the twisted strip containing two v-shaped cuts under the same conditions, this was 2.40. Increasing the number of cuts on the twisted strip (sample 3) improved the efficiency of the SC and decreased the pressure drop. In regard to the case of sample 3, at Re = 10000 and φ = 1%, the efficiency was increased by 2.22%, while the pressure drop was decreased by 4%.